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Copyright>        Copyright (C) 1986-2024 Altair Engineering Inc.
Copyright>
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Copyright>
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Chd|====================================================================
Chd|  PRINC_U1                      source/materials/mat/mat001/princ_u1.F
Chd|-- called by -----------
Chd|        M1ISMSTR11                    source/materials/mat/mat001/m1ismstr11.F
Chd|-- calls ---------------
Chd|        VALPVECOP_V                   source/materials/mat/mat033/sigeps33.F
Chd|====================================================================
              SUBROUTINE PRINC_U1(
     1                            NEL   , ES1 , ES2 ,ES3 ,ES4 ,
     2                            ES5   ,ES6  ,EV   , DIRPRV  )
C-----------------------------------------------
C   I M P L I C I T   T Y P E S
C-----------------------------------------------
#include "implicit_f.inc"
C-----------------------------------------------
C   G L O B A L   P A R A M E T E R S
C-----------------------------------------------
#include      "mvsiz_p.inc"
C-----------------------------------------------
C   C O M M O N 
C-----------------------------------------------
C----------------------------------------------------------------
C  I N P U T   A R G U M E N T S
C----------------------------------------------------------------
      INTEGER       NEL     
      my_real
     .   ES1(MVSIZ), ES2(MVSIZ), ES3(MVSIZ), 
     .   ES4(MVSIZ), ES5(MVSIZ), ES6(MVSIZ),
     .   EV(MVSIZ,3),DIRPRV(MVSIZ,3,3)
C----------------------------------------------------------------
C  L O C A L  V A R I B L E S
C----------------------------------------------------------------
      INTEGER    I,J,K
      my_real
     .            AV(MVSIZ,6),EVV(MVSIZ,3)
C----------------------------------------------------------------
C--------- [B]=[F][F]^t -1 strain-----
      DO I=1,NEL
       AV(I,1) = ES1(I)
       AV(I,2) = ES2(I)
       AV(I,3) = ES3(I)
       AV(I,4) = ES4(I)
       AV(I,5) = ES5(I)
       AV(I,6) = ES6(I)
      ENDDO
        CALL VALPVECOP_V(AV,EVV,DIRPRV,NEL)

      DO I=1,NEL
        EV(I,1:3)=SQRT(MAX(ZERO,(EVV(I,1:3)+ ONE))) - ONE
      ENDDO
C----------------
C      
      RETURN
      END
